Can we include condition as an argument in custom functions? - php

Question

Suppose I have a multidimensional array
$num1 = array(1, 4, 6, 12, 15, 16, 21, 34, 25, 29);
$num2 = array(1, 5, 18, 19, 23, 19, 23, 45, 23, 16);
$array = array($num1, $num2);
I want to extract all the values from $array where the $array[0] values meet some condition e.g. have a value between 10 & 20.
to get the required values from $array I can use this code:
$count = count($array[0]);
$new_array = array_fill(0, $count, array());
for($i = 0; $i < $count; $i++)
{
if($array[0][$i] >= 10 && $array[0][$i] <= 20)
{
$new_array[0][] = $array[0][$i];
$new_array[1][] = $array[1][$i];
}
}
//I get the array that I need
print_r($new_array);
This is the code I need to change every time
$array[0][$i] >= 10 && $array[0][$i] <= 20 (condition --> values from the first sub array are >= 10 and <= 20)
result would be
Array(0 => Array(0 => 12, 1 => 15, 2 => 16), 1 => Array(0 => 19, 1 => 23, 2 => 19))
another condition
$array[1][$i] >= 20 && $array[1][$i] <= 30 (condition --> values from the second sub array are >= 20 and <= 30)
result would be
Array(0 => Array(0 => 15, 1 => 21, 2 => 25), 1 => Array(0 => 23, 1 => 23, 2 => 23))
I need to do such operations with different columns using different conditions. So, instead of writing code for looping every time, I want to create a function with condition as an argument. Is it possible, if so how?
I would like to have a function with three arguments as shown below
function_name ($array, $column_num, $condition)
Any alternative solutions are also welcome.... :)
Code I used finally to get this done....
<?php
function mdarray_condition_extract($array, $column, $condition)
{
$count = count($array[0]);
$nsac = count($array);
$new_array = array_fill(0, $nsac, array());
for ($i = 0; $i < $count; $i++)
{
$valToTest = $array[$column][$i];
if ($condition($valToTest))
{
for($k = 0; $k < $nsac; $k++)
{
$new_array[$k][] = $array[$k][$i];
}
}
}
return $new_array;
}
$array = array(array(1, 4, 6, 12, 15, 16), array(1, 5, 18, 19, 23, 19));
$columns = array(0,1,0);
$conditions = [
0 => function($val){return $val >= 10 && $val <= 20;},
1 => function($val){return $val >= 20 && $val <= 30;},
2 => function($val){return $val == 6 || $val == 20;}
];
$combo = array($columns, $conditions);
$condcount = count($combo[0]);
for($i = 0; $i < $condcount; $i++)
{
print_r(mdarray_condition_extract($array, $combo[0][$i], $combo[1][$i])); echo "<br><br>";
}
?>
Thanks all for the response, it helped me in a great way...!!

Answer 1

Your existing code is very close.
function filterParallelArrays($array, $predicateFilterIndex, $predicate)
{
$count = count($array[0]);
$new_array = array_fill(0, $count, array());
for ($i = 0; $i < $count; $i++)
{
$valToTest = $array[$predicateFilterIndex][$i];
if ($predicate($valToTest))
{
$new_array[0][] = $array[0][$i];
$new_array[1][] = $array[1][$i];
}
}
return $new_array;
}
$predicate = function($val)
{
return $val >= 10 && $val <= 20;
};
print_r(filterParallelArrays($array, 0, $predicate));

Answer 2

You question is about filtering your arrays. For that, PHP has built-in function array_filter() . It takes callback for filtering values.
If I got your question correctly, you want to apply filter to your sub-arrays - and, probably, with different conditions. Normally, if do that statically, it is:
$array[0] = array_filter($array[0], function($x)
{
return $x>=10 && $x<=20; //item between 10 and 20
});
-but if you have predefined list for each column, you can fill a map:
$conditions = [
//column index => condition callback:
0 => function($x){ return $x>=10 && $x<=20; },
1 => function($x){ return $x==50 || $x==80; },
//e t.c.
];
foreach($array as $key=>$column)
{
if(array_key_exists($key, $conditions))
{
$array[$key] = array_filter($array[$key], $conditions[$key]);
}
}
So, using array_filter() - you can do it natively, I think you won't need your own custom function to do this (because wrapping native function has little sense in this case).

Answer 3

Given your latest update, you could do something like this. But I'm still not really sure what your objective is here, so this might be totally out to lunch.
function array_function($key, $lcond, $rcond)
{
$count = count($array[0]);
$new_array = array_fill(0, $count, array());
for($i = 0; $i < $count; $i++)
{
if($array[$key][$i] >= $lcond && $array[$key][$i] <= $rcond)
{
$new_array[0][] = $array[0][$i];
$new_array[1][] = $array[$key][$i];
}
}
//I get the array that I need
return $new_array;
}